Since its invention in the nineteenth century, the traditional long afterglow luminescent material of ZnS series has been undergoing continuous improvement, and several typical products have been developed, such as ZnS:Cu (which emits green light), (CaSr)S:Bi (which emits blue light), and (ZnCd)S:Cu (which emits orange yellow light), and have been applied in some commercial fields, however these materials have some defects, such as poor stability, prone to decompose in air, prone to turn gray and even dark in color under sun shine, short luminescence afterglow time which is generally within 0.5 to 2 hours, and low luminescent brightness etc., and can not meet the requirement of practical use. In order to improve the brightness and the afterglow time of these materials, radioactive elements such as Co, Ra, H3 have been added into these materials to produce long afterglow luminescent materials with radioactivity. Such materials can give out light continuously and have ever been used in the fields of aircraft instrument, clocks etc., however their applications were greatly confined because of the radioactive contamination and high cost.
Long afterglow luminescent materials of aluminate system were invented at the beginning 1990s, as described in China patent ZL92110744, ZL98109570.4, ZL 95118116.5, U.S. Pat. Nos. 5,376,303, 5,424,006, their luminescent brightness, long afterglow property and stability were remarkably superior to the sulfide series products described above, and the materials have been used in daily goods, safety marks, clocks etc. However the long afterglow luminescent materials of aluminate system described above still suffer from some disadvantages in practical applications, such as    1. Short afterglow time: the prior art long afterglow luminescent materials of aluminate system have a nominal afterglow time over 24 hours, which however is determined based on the final luminescence intensity equivalent to the brilliance of 0.3 mcd/m2. In fact, the identification capability of naked eyes is very weak under such brilliance, and the application of the long afterglow luminescence materials is greatly limited.    2. Poor applicability: a luminescent material with high brilliance does not necessarily mean the products made with, the luminescent material have high brilliance. The brilliance of a luminescent product depends to a great extent on the matching of the luminescent material with the medium for manufacturing the luminescent product. Many luminescent products can not meet the requirements of various applications, and in practical applications, most of the luminescent materials were used after being fabricated into products.    3. Fast charge is impossible: the light absorption rate of the long afterglow luminescent material prepared by the prior art is slow, and very difficult to reach saturation, which results in that the luminescence intensity and afterglow time of the luminescent materials and the luminescent products can not meet the requirements of practical use well.    4. Lacking of variety in luminescence color: the luminescence color suffers from lacking of variety, and if it is desired to realize multiple colors (peak wavelength of emission spectrum: 440-620 nm), it is necessary to utilize a number of luminescent materials of different systems. It is still unavailable for luminescent materials of the same system realizing multi-color luminescence.